This may be achieved directly or through a heat exchanger.

The tank has a built in heat exchanger to heat domestic cold water.

Many metal collectors are installed as part of a sealed heat exchanger system.

Radiators and convectors are heat exchangers designed to transfer thermal energy from one medium to another for the purpose of space heating.

After being heated in the panels, the HTF travels to the heat exchanger, where its heat is transferred to the potable water.

However, instead of exhausting this air, the dryer uses a heat exchanger to cool the air and condense the water vapor into either a drain pipe or a collection tank.

We figured out how to put a vapor compression distiller on this thing, with a counter flow heat exchanger to take the waste heat, then using a little bit of the electricity control that process, and for 450 watts, which is a little more than half of its waste heat, it will make 10 gallons an hour of distilled water from anything that comes into it to cool it.